CaseKeyPaths and the ForEachStore

[seanmrich]

I created a toy project that manages color palettes using the new Reducer macro and CaseKeyPaths. I'm getting an error when scoping a ForEachStore. Here's the relevant reducers:

@Reducer
public struct PaletteEditor: Reducer {
  public struct State: Equatable {
    public var colors: IdentifiedArrayOf<PaletteColor.State>
  }
  
  public enum Action {
    case colors(IdentifiedActionOf<PaletteColor>)
  }
  
  public var body: some Reducer<State, Action> {
    Reduce { state, action in
      switch action {
      case .colors:
        return .none
      }
    }
    .forEach(\.colors, action: \.colors) {
      PaletteColor()
    }
  }
}

@Reducer
public struct PaletteColor {
  public struct State: Equatable, Identifiable {
    public var color: RGB
    public var id: ID
    
    public init(color: RGB, id: UUID? = nil) {
      self.color = color
      self.id = {
        if let id { return Tagged(id) }
        @Dependency(\.uuid) var uuid
        return Tagged(uuid())
      }()
    }
    
    public typealias ID = Tagged<Self, UUID>
  }
  
  public enum Action {}
  
  public var body: some Reducer<State, Action> {
    EmptyReducer()
  }
}

Then in the view for the palette, I get an error at the action keyPath: "Reference to member colors cannot be resolved without a contextual type"

public struct PaletteEditorView: View {
  let store: StoreOf<PaletteEditor>
  
  public var body: some View {
    ForEachStore(store.scope(state: \.colors, action: \.colors)) { colorStore in
    //                                                ^ Error 
      PaletteColorView(store: colorStore)
    }
  }
}

I tried fully qualifying the keyPath (perhaps wrongly) with \PaletteEditor.Action.Cases.colors but I just get "Failed to produce diagnostic" on the View. I referenced the 1.4 documentation on migrating to the new CaseKeyPaths as well as the ForEachStore but I'm not seeing where I went wrong. I'd sure appreciate any guidance you have.

[mbrandonw]

Hi @seanmrich, the tools you are wanting to use are not released in 1.4. They are still in beta, which you can find the details here. If you want to try it out you will need to point your dependency on TCA to the branch store-tree. We will be releasing the tools in the next few days.

[seanmrich]

Well, that would explain it 🤦‍♂️.

Separately, if I turn on strict concurrency I get a warning about the action key path in PaletteEditor.body's forEach method:
"Cannot form key path that captures non-sendable type 'KeyPath<PaletteEditor.Action.AllCasePaths, AnyCasePath<PaletteEditor.Action, IdentifiedAction<PaletteColor.State.ID, PaletteColor.Action>>>' (aka 'KeyPath<PaletteEditor.Action.AllCasePaths, AnyCasePath<PaletteEditor.Action, IdentifiedAction<Tagged<PaletteColor.State, UUID>, PaletteColor.Action>>>')"

I tried setting both PaletteEditor.Action and PaletteColor.Action to explicitly conform to Sendable, but it's the KeyPath itself that isn't Sendable. Looking at the code for the for each reducer, I don't see a Sendable requirement so I'm not sure what the warning is addressing.

[mbrandonw]

That is a known issue in the swift compiler and it should be fixed very soon. You will have to ignore that warning for now.

[seanmrich]

Excellent. Thanks for the guidance!